Need 2 Know Kelp/Seaweed Benefits

I've been wondering about the Pro's of using Kelp/Seaweed extracts lately but would really like to know it's real purpose and how its used. If someone that has used it could shed some light on the subject the info would be much appreciated.

What is the biggest benefit of using Seaweed/Kelp extracts?

What phase should it be used in veg or flower?

Should it be used as a foliar spray or actual nute supplement in your res mixture????

And finally what brand should I look for???

I just started adding Maxicrop liquid seaweed four weeks ago. I use in veg and bloom, in my res mix and have noticed a more deep deeeeeep green. From what I understand, it helps with breaking down the intake. Cheapest additive I have, has made the most visible difference.
still learning..

http://voices.yahoo.com/the-benefits-kelp-garden-5987170.html
http://www.acadianseaplants.com/plant-growth-development-products/soil
http://www.gardenerspantry.ca/blog/kelp-fertilizer.html